is there any way of getting a build sheet for my 70 chevelle??

Unless your car was built in canada, there is no way to get any documents for your car. GM did not keep records of build sheets.

If you have one it's buried somewhere in your car.

Even the cars made in Canada cannot get a build sheet. What they provide comes from shipping records transferred to GM letter head.

No means exist to produce an original build sheet because nothing was saved.